The present invention relates to a semiconductor laser device and a method for fabricating the semiconductor laser device, and more particularly relates to a semiconductor laser device for an optical pickup light source used in an optical information processing device such as an optical disk system and a method for fabricating the semiconductor laser device.
As a light source for a next generation high-density optical disk, there is a strong demand for a laser light source in the blue-violet region, which emits light in the short wave region (i.e., the 400 nm region) which allows reduction in a focusing spot diameter on an optical disk, compared to light in the red region and the infrared region, and is effective in improving reproduction and information-packing density of an optical disk.
To achieve laser light in the blue-violet region, research and development of semiconductor laser devices using III-V nitride semiconductor containing gallium nitride (GaN) as a main component has been vigorously conducted. In view of the above-described application of a high-density optical disk, a high power blue-violet semiconductor laser device which is capable of handling a high information-recording density is desired to be achieved. Under present circumstances, a light output of at least 65 mW or more is considered to be necessary in pulse oscillation. Furthermore, to realize high-speed writing, a high output characteristic which allows an output of 30 mW or more in continuous wave oscillation is desired.
FIG. 18 is a cross-sectional view illustrating a known nitride semiconductor laser device described in Japanese Laid-Open Publication No. 2000-299528. As shown in FIG. 18, the known nitride semiconductor laser device includes an n-type cladding layer 151, an active layer 152, a p-type cladding layer 112 having a ridge portion 112a in upper part thereof, and a p-type contact layer 101 provided on the ridge portion 112a are formed in this order on a substrate 150 of sapphire by epitaxial growth. A first electrode layer 113 is formed on the p-type contact layer 101. On an upper surface of the p-type cladding layer 112 and side surfaces of the ridge portion 112a as well as side surfaces of the p-type contact layer 101 and the first electrode layer 113, a dielectric film 102 of silicon oxide, i.e., a current confinement layer is formed and then a second electrode layer 114 is formed thereon. Thus, a semiconductor laser device having a waveguide structure exhibiting the current confinement function and the light trapping function can be achieved.